When Jesus Christ calls us to come follow Him, we leave our old life behind and become a new man in Christ. The new creature we become receives a new name revealed to us by God. The purpose of the new name is to separate us from our old life of bondage. We are not the same person after Jesus Christ calls us out of the world to be His ambassadors.
17Therefore, if anyone is in Christ, he is a new creation; the old has gone, the new has come!
2 Corinthians 5:17
We believe we must start a new life with a new identity. Our scriptural foundation is John, Chapter 3:
3Unless a man has been born over again he cannot see the kingdom of God . . . 5In truth I tell you, no one can enter the kingdom of God without being born from water and spirit. 6Flesh can give birth only to flesh; it is spirit that gives birth to spirit.
John 3:3, 5, 6
Our name changes because God renames us. There is no intent to defraud or deceive anyone. Many men and women in the Bible were given new names by the Lord. Some notable examples from the Bible are Abram became Abraham, Sarai became Sarah, and Jacob became Israel. Two famous New Testament name changes occurred when Jesus named Simon-Cephas (Peter) and Saul of Tarsus became Apostle Paul:
When Simon the fisherman was introduced to the Messiah, the Lord immediately recognized the latent power of the fisherman and gave him the name of Cephas (Peter) which means "the rock."15 When Peter displayed weakness, Jesus addressed him by his old surname rather than by the name that meant "rock."16
Saul was the man who persecuted Christ's followers, breathing murderous threats against the disciples of the Lord. He applied to the High Priest for letters authorizing him to arrest anyone he found who followed the new way. On his way to Damascus, he had a vision in which Jesus Christ asked, "Saul, Saul, why do you persecute me?" Shortly after his vision, Saul of the Pharisees became Paul of the Nazarenes. The great persecutor of Christ became the great Apostle of Christ.17
The fact that we change our names because God renames us is not something unusual. Besides the Biblical name changes, it is also common practice for monks and nuns to take new names when they join a religious order. Popes change their names when they are elected. Cassius Clay is a famous example of a man having a religious conversion and changing his name to Muhammad Ali.
All of these people who changed their names for religious reasons did so because they felt God was calling them to a new life and a new identity.
15 - John 1:41,42; Matthew 16:16-18
16 - Luke 22:31; Mark 14:37; John 21:15-17
17 - Acts 9:1-4; Acts 13:9